Hi Paul,
I agree with Shibui - looking at the pics, it’s moss and it’s
NOT the problem, but rather an indicator in my opinion - its not looking too good! We’ve been growing a few serissas over the years from very small to medium size, because we just love the different varieties and sizes.
Back to your problem, it looks to us that your plant is
too wet and hence the growth of that type of moss - like a matt, there are many different kinds of moss and as Shibui said aren’t a problem on trunks or branches. You can use a
wet toothbrush to clean it off rather than a dry one, which can be rough on the bark.
Three issues are most important in growing serissa - light, water and fast draining soil! I’ve attached a link of an article in our newsletter which I wrote based on the experiences we’ve made.
http://www.yarravalleybonsai.org.au/new ... 2%20R1.pdf
Immediate action - take your plant carefully out of the pot, check the roots and
ONLY remove any rotten ones - don't disturb the root ball too much and slip-pot into a larger orchid growing plastic pot with a
fast draining mix and hope for the best!
No fertilising, but a bid of Seasol!!!
Hope that this is of some help?!
Regards,
Rudi